Air traffic control tower and radar simulator (solo + multi-player)
FSKneeboard adds a helpful ingame panel to your flight simulator
Precision Trigonometry: Advanced Calculator for Complex Math
Open pharmacovigilance data extraction, mining and analysis tool
Speaking Air Traffic Controller Simulator for Flightgear
VR-Optimized ATC/Radio Plugin for X-Plane + FlyWithLua
Controller-Pilot Data Link Simulator for procedural and radar training
BlueSky Open Air Traffic sim, (Windows/Linux/Mac, Python 2.x based)
A server to exchange flightplan information between ATCs
Air Traffic Controll Simulator (ICS Project)